1. Field of the Invention
The present invention relates to a composite filter and a radio communication apparatus. In particular, the present invention relates to a composite filter comprising a surface acoustic wave filter and an LC filter, and a radio communication apparatus using the composite filter.
2. Description of Related Art
In FIG. 8, a RF block diagram of a portable telephone terminal which is an example of a general radio communication apparatus is shown. The portable telephone terminal operating in a single frequency band such as 800 MHz, 1.5 GHz, etc. includes an antenna ANT, a duplexer for antenna DPX, a transmitting RF portion Tx, a receiving RF portion Rx, and a synthesizer portion SYN. The input portion of the transmitting RF portion Tx is connected to a modulator portion MOD, and the output portion of the receiving RF portion Rx is connected to a demodulator portion DE respectively. The transmitting RF portion Tx is composed of a high output amplifier PA, a buffer amplifier BA, band-pass filters F1, F2, a low-pass filter F3, and a mixer MIX1, and performs a function to output a transmitting signal in receipt from the modulator MOD to the antenna ANT through the duplexer for antenna DPX. On the other hand, the receiving RF portion Rx is composed of a low-noise amplifier LNA, band-pass filters F4, F5, and a mixer MIX2, and caries out a function to output a receiving signal received from the antenna ANT through the duplexer for antenna DPX to the demodulator DE.
And, a conventional portable telephone terminal has been built up in such a way that, although not illustrated, a circuit board made of glass-epoxy resin, ceramics etc., has the various amplifiers PA, BA, LNA formed as chip-parts, a duplexer for antenna DPX made up of dielectric filters, and each of filters F1 through F5 mounted thereon.
However, in the above-mentioned portable telephone terminal making each of the conventional components as a chip-component has led to greater integration and this integration has increased the number of parts and has complicated the assembly process.